The proposed research is an analysis of processes involved in the development of preimplantation embryos. The main goal is to further our understanding of developmentally important relationships between microenvironmental clues, the cells' plasmalemma, and their genomic response. Plasmalemmal glycoconjugates are developmentally regulated and likely to be involved in these interactions. The proposed studies aim at (1) determining if plasmalemmal glycoconjugates change with the cells' position in the embryos, (2) determining the nature and the identity of developmentally regulated glycoconjugates (3) studying the importance in embryogenesis of certain glycoconjugates (using glycosylation inhibitors), (4) determining if changes in plasmalemmal glycoconjugates require transcription of previously inactive genes (using transcription blockers). Composition and nature of plasmalemmal glycoconjugates will be determined, (1) by labeling preimplantation embryos with electron dense probes for carbohydrates (ferritin-conjugated lectins) and quantifying them at the electron microscopic level, in some cases following enzymatic digestion or extraction of the plasmalemma, and (2) by two-dimensional gel electrophoresis by glycoconjugate extracts of the plasma membrane. This work should enable us to ientify plasmalemmal components that are involved in mechanisms of cell differentiation and embryogenesis.